The overall aim is to understand the biosynthesis of collagen fibers. The function of collagen V is unknown. Our discovery of procollagen V showed similarities with interstitial collagens in molecular length and processing of propeptides, but uncovered significant new features which we shall now investigate. The long-lived intermediate p-collagen (V) and the final collagen V both retain larage non-collagenous peptides. We shall characterize them, their interactions with the unusual "P-peptides" to which the intermediate becomes linked, and their potential, interesting role as linkers between fibers, cell surfaces and basement membranes. We have found a new procollagen V chain which seems to be specific for tendon. Its molecular function will be studied relative to the differential fiber structure of the core and gliding surfaces of tendons and of tendon sheaths, and its production by cells derived from these different regions. This information will help in wound healing of resected tendons. We shall determine the forms of procollagen I and their state of molecular association when they exit from fibroblasts and deposit on nascent fibers. Supramolecular assembly of extracellular matrix depends on the concentrations of the interacting components. We shall study how far molecular exclusion effects critically change the effective concentrations. In chick embryo blood vessels we found a new collagenous peptide. We will isolate it, compare it with the recently described "intima" collagen VI, and follow its assembly. This is of importance to finding new molecular arrangements in fibrous collagens. We shall combine biosynthetic, immunological and molecular electron microscopic approaches to follow extracellular matrix assembly.